1. Field of the Invention
The present invention relates to a sprue dowel having a radically projecting, embeddable portion and an attachment portion that is formed as a hollow cylindrical shaft, and used for a mutual extension-proof connection of two solid bodies in a concrete-to-concrete connection.
2. Description of the Prior Art
For form- and forcelocking connection of a first solid body, e.g., old or mature concrete, with a free-flowing, later hardenable, second solid body, e.g., new or young concrete, a connector or a sprue dowel is secured with its attachment portion by a temporarily free-flowing, hardenable substance, e.g., grout or thermosetting resin mortar, in a blind bore formed in the first solid body, and is embedded with its radially projecting, embeddable portion in the second solid body that has not yet hardened enough.
As a connector for both solid bodies, e.g., a reinforcing iron, which is offset on the site, has its end preliminary conically upset, or is formed on the site, is used. The reinforcing iron is fixed in the blind bore in the first solid body with a temporarily free-flowing, hardenable substance. A second solid body, which is engageable with the first solid body, can be secured on the cast reinforcing iron. Alternatively to the reinforcing iron, threaded rods with a top plate screwable thereon can be used. The drawback of these solutions consists in that the connector should be held in a straight position until the temporarily free-flowing, hardenable substance completely hardens. Within this time period the connector cannot be loaded. The preliminary work, the setting process and the necessary by works are time-consuming and cost-intensive.
German Publication DE 31 07 718 A1 discloses a holding pin formed of an elongate tube with longitudinal grooves and having a tapering end. The other diameter of the pin is greater than the diameter of the blind bore. To simplify driving of the pin in, there is provided a guide plate with an opening having a diameter smaller than that of the blind bore. The tube, upon being driven in, is pressed through the opening of the guide plate and becomes secured in the blind bore by friction that is produced between the tube and the blind bore wall. The drawback of the holding pin of DE 31 07 718 A1 consists in that a guide plate is needed for setting the holding pin. Without the guide plate, in most cases, the friction between the pin and blind bore wall prevents the pin from reaching a required depth.
German Publication DE 22 05 289 A1 discloses an anchor which is formed of a plastic material and is set by using a temporarily free-flowing, hardenable substance that fills the blind bore. On its outer surface, the anchor is provided with elastically deformable longitudinal ribs. When the anchor is driven in the bore, the deformable ribs become jammed in the blind bore wall. The drawback of this anchor consists in that it can withstand only small tensioning and compression forces before the substance become hardened.
German Publication DE 100 52 810 A1 discloses a sprue dowel which is formed of a circumferentially closed, regionwise radially indented tubular section.
German Publication DE 101 03 231 A1 discloses a similar sprue dowel that in addition is provided with a conical sleeve within its embeddable portion. The sprue dowel is set in a blind bore and is adjusted. After the dowel has been set, the blind bore is filled with a temporarily free-flowing hardenable substance. The sprue dowel of 100 52 810 A1 and that of DE 101 03 231 A1 both favorably proved themselves in practice. However, these sprue dowels cannot be subjected to a load immediately after being set and before the temporarily free-flowing, hardenable substance hardens. E.g., if reinforcement elements of the second solid body, which are securable on the sprue dowel, should become accessible right away, it can lead to maladjustment of the already straightened dowel during the hardening of the temporarily free-flowing, hardenable substance.
Accordingly, an object of the invention is a sprue dowel that can be subjected to a load even before the bore is filled with a temporarily free-flowing, hardenable substance and during the hardening of the substance.